The following shall constitute a prior art statement under the guidelines as set forth in 37CFR Sections 1.56, 1.97 and 1.98.
The fabrication of tools for cutting, crushing or breaking hard materials such as rock has long been a problem. Many materials which are hard enough to successfully abrade rock formations such as metal carbides, silicides, borides, tellurides and the like are difficult to use because, despite their high hardness, they are extremely brittle and easily shattered upon impact.
In an attempt to overcome the difficulties associated with the brittleness of these hard abrasive materials, it has become common to form particulate hard abrasive material in a matrix of a softer, tougher metal. Thus, U.S. Pat. Nos. 1,549,615, 1,721,416 and 1,993,598, describe processes whereby various hard abrasive particulate materials such as tungsten carbide are cemented in a composite containing up to about 20% of a softer, tougher metal such as iron, nickel and/or cobalt. Such composites are then utilized directly for the cutting or abrading faces of a tool such as a drill bit as described in U.S. Pat. No. 3,120,285 or an abrasive compact such as described in U.S. Pat. Nos. 3,879,901 and 4,063,909. Alternatively, welding rods have been formulated either of a cemented hard abrasive material or incorporating metal powders which will form a cemented hard abrasive material in the weld arc to deposit the cemented, hard abrasive material on the desired surface of a cutting tool such as described in U.S. Pat. Nos. 1,757,601 and 3,385,683.
Erosion of the softer metal with the consequent spalling of the hard abrasive particles has led to the development of cutting and abrasive tools which utilize filamentary or rod-like forms of hard abrasive material on cutting tool surfaces. Thus, an abrasive hone is disclosed in U.S. Pat. No. 3,972,161, in which cylindrical fibers of hard abrasive materials such as metal nitrides, carbides and borides are oriented parallel to each other and generally perpendicular to the honing surface with a surrounding matrix of wearable material. Similar structures are disclosed in U.S. Pat. Nos. 4,116,688 and 4,295,885.
In a similar manner, U.S. Pat. Nos. 1,855,330 and 4,262,761, describe the use of tungsten carbide rods embedded in the cutting edges of a cutting tool such as a rock bit tooth. When a portion of the brittle tungsten carbide rods are broken off, the surrounding material wears down to expose the broken end of the rod which then continues the cutting process until further broken and finally worn away completely.
U.S. Pat. No. 4,299,297, describes a rotary percussion bit having a plurality of raised cutting elements. The cutting elements comprise discs of hard abrasive material embedded in a tougher, softer wearable filler material disposed within rings of metal which are attached to the face of the rotary percussion bit. Any impact against the hard abrasive discs of the cutting elements can cause breakage and loss of the abrasive material from the cutting surface.